Lead-free perovskite based bismuth for solar cells absorbers

Structural, electronic and optical absorption spectrum properties of lead free organometal halide perovskite CH3NH3BiX3 (X = I2Te, I2S, I2Se) as a new absorber for solar cells are studied in comparison to the well-known methylammonium lead iodide perovskite (CH3NH3PbI3) by using first principle calculations. CH3NH3PbI3 is known to be one of the major breakthrough in absorbing layers for solar cell material researches. These properties allowed this material to break records in the photoelectric conversion reaching 22% in Power Conversion Efficiency (PCE) in a short period of time, but this material have some drawbacks, putting obstacles for its commercialization. First one is the instability and the second one is the toxicity of lead. It was the reason why, the choice of Bi was the most appropriate to use in CH3NH3BiI2Te, CH3NH3BiI2S and CH3NH3BiI2Se as it is a non-toxic element and also for the fact that it does not induce a big difference in the electronic structure, being close to lead in the periodic table. Furthermore, for its high optical absorption in the visible obtained on CH3NH3BiI2Te, CH3NH3BiI2S and CH3NH3BiI2Se compounds. These advantages may suggest that halide perovskite CH3NH3BiX3 (X = I2Te, I2S, I2Se) based bismuth could be a promising alternative to CH3NH3PbI3. These results may provide a basis for future applications in photovoltaic domain.